Ah, i get it. i just read your other post. Go through the whole system and clean the carbs. Take them (3) off and clean them. The best way is to take one at a time and dismantle it, just in case you forget, you have to others to look at. Then, soak them in carb cleaner all night long. This is more of a precatuion. Then go to the web or dealer and get a picture, illustrated diagram of you specific carbs (this is also a learning process for general purpose) and find the idle screw and air screw. Idle screw is self explanitory and isnt the cause of your problem, but it is good to know. Adjust all air screws in all the way and then ride it. Gun the engine and slowly turn the air screws out 1/4 turn untill it takes off just as you want it. When you start to feel the engine get worse after turing, turn it back 1/4 and then you are at the peak. Now i can't remember for sure, but i think there is a high end adjustment also, hold on, let me check the racing manual for my 99'.......What is really the decider is what kind of carbs you have. There are Mikuni and Keihin in most polaris models. Ok i checked, no high end screws. Um.. it sounds like the engine is running to rich or lean at high end. Reaplace all the plugs, claean the entire fuel system (carbs too) make the previously discussed adjustments and get back to me. If it is still giving you crap, tell me and i will have a few further ideas. I know cleaning up the low end doesnt seem related to your problem, but go from there to make sure the engine is getting the fuel and air it needs. It sounds like it isn't getting it.
best of luck
dano
p.s let me know how it works